I would have. I actually wished they had came out of one, or at least between the size of 5S and 6. But instead, we just got a 6S and 6S+. So, after two years, I had to upgrade because the battery life on the 5S was ridiculously slow, and I was missing out on features like Apple Pay, etc.
I find the 6S (as with the 6) to be too big. I've already dropped it three times because it's easy to fumble.. I have small hands. It is hard to use the phone with just one hand, whereas the 5S was no problem.
I mainly use the iPhone as a phone and do not need any bigger of a screen. I understand, a lot of users use the phones for everything from games to movies/tv shows, etc. It's just too big to me.
This was the only iPhone I was not excited to have. I do like the upgrade in performance and capabilities, it's a great phone. Just not completely content.